1. Field of the Invention
The present invention is directed to electrical muscle stimulators and more particularly to such stimulators used to assist in stabilizing musculature of the knee in users having inadequate neurological and muscular control to obtain normal locomotion.
2. Prior Art Statement
It has been recognized for some years that electrical stimulation of a muscle can effectively cause muscular contraction or reaction which will aid to performing some bodily functions which could not have been otherwise achieved in patients and users having certain types of neurological and muscular deficiencies. Thus, devices have been developed to stimulate leg and arm muscles which provide electrical pulses in response to intelligently controlled or automatically controlled switches.
U.S. Pat. No. 2,737,183 issued to Charles Giaimo describes an electrical control device for partially denervated muscles. The device is a basic dry cell pack with electrical stimulation, through electrodes, to leg muscles. The user merely presses the switch when muscle stimulation is needed. The stimulation causes muscle reaction so as to effectuate leg movement in the forward direction to take a step. The manual switch may be automatic and be responsive to tilting, such as with a mercury switch.
U.S. Pat. Nos. 3,083,712 and 3,344,794 are both directed to devices for electrical stimulation of leg muscles wherein electrical pulses are activated in response to the closing of a circuit by a heel switch. In U.S. Pat. No. 3,083,712 to James Keegan, Jr., when pressure is placed on the heel, the switch is closed, a circuit is completed, current builds up in a capacitor and timely pulses are sent to muscles for stimulation via electrodes. In U.S. Pat. No. 3,344,794 to F. F. Offner et al, a similar system is shown except that pressure on the heel opens the circuit and pulse stimulation is interrupted. Thus, these two patents suggest opposite basis for pulse stimulation, i.e. heel on the ground and heel off the ground.
U.S. Pat. No. 3,083,712 to James Keegan, Jr. also describes alternative pulse control mechanisms such as a leg-strapped mercury switch which responds to a certain level of tilting, and the use of timing mechanisms to control sequential or spaced pulses to various electrode sites.
U.S. Pat. No. 4,005,296 to Robert Olson describes a specific disc switch for the heel for control of electrical muscle stimulation wherein the pulsing occurs only when the heel is off the ground. U.S. Pat. No. 3,881,496 to Jakob Vredenbregt et al acknowledges known heel control methods, and points out that when lifting the foot activated pulses are initiated but the heel switch exhibits deviations from natural locomotive patterns sometimes causing balance problems. This patent suggests that pressure changes at the ball of the foot be used as the parameter for initiating and ceasing pulsation.
Although not directed to the stimulation of muscles for locomotion by body part positions alone, U.S. Pat. No. Reissue 32,091 to David J. Stanton, is directed to a dual channel neuromuscular stimulator which involves complex computerization and wiring and either technician or second person operator control or heel switch stimulation.
U.S. Pat. No. 4,569,352 to Jerrold Petrofsky describes a very complex electrical and mechanical device for feedback control of movement for standing and for walking of paraplegics and quadriplegics. Complex electrical stimulation and control of hips, knees an ankles is described using external hip to knee metal rods, mechanical knee restriction supports and controlled angle and foot attachments. Various movable body mechanisms are locked and unlocked from position to position while muscle control with electrical pulse is employed. This device is extremely advanced and would likely be beyond the cost of most para- and quadriplegics and could not be strapped to or carried by the user.
Thus, the prior art is believed to establish that portable stimulators have been developed using different theories of when stimulation should occur and how controls should be applied to the body. Non-portable and complex computerized systems have been developed but may be beyond the reach of the typical person needing help and may be restricted by size, weight, complexity and the need for a qualified operator.
The present invention, on the other hand, represents a significant discovery in muscle stimulation for locomotive assistance by using simultaneous switches for both knee angle and heel contact to restrict the initiation, ceasation and timing of electrical pulse stimulation without the need for computerization or sophisticated, non-portable equipment.